ScienceShot

ScienceShot: A Moon-Maker Among Saturn's Rings

One of Saturn's smallest moons is creating tiny moons of its own as it whizzes around the gas giant. According to photos snapped by the orbiting Cassini spacecraft, Prometheus's gravity is disturbing icy particles in Saturn's F ring. The resulting ripples spread across the ring, as seen in this mosaic of images, and help the particles clump into giant snowballs up to 20 kilometers in diameter. Some of the snowballs get ripped apart by subsequent passes of Prometheus. But as scientists report online this month in The Astrophysical Journal Letters, some manage to hang together a little longer. It's a tenuous and chaotic process, but it's the first time anyone has observed moon making in action.